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WO2025059483A1 - Dispositifs de pompage d'ions électrochimiques et leurs procédés d'utilisation - Google Patents

Dispositifs de pompage d'ions électrochimiques et leurs procédés d'utilisation Download PDF

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WO2025059483A1
WO2025059483A1 PCT/US2024/046645 US2024046645W WO2025059483A1 WO 2025059483 A1 WO2025059483 A1 WO 2025059483A1 US 2024046645 W US2024046645 W US 2024046645W WO 2025059483 A1 WO2025059483 A1 WO 2025059483A1
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electrode
cation
circuit
solution
anion
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Shihong Lin
Longqian XU
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Vanderbilt University
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Vanderbilt University
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B26/00—Obtaining alkali, alkaline earth metals or magnesium
    • C22B26/10—Obtaining alkali metals
    • C22B26/12—Obtaining lithium
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B23/00—Obtaining nickel or cobalt
    • C22B23/04—Obtaining nickel or cobalt by wet processes
    • C22B23/0453—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B23/0461—Treatment or purification of solutions, e.g. obtained by leaching by chemical methods
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B3/22—Treatment or purification of solutions, e.g. obtained by leaching by physical processes, e.g. by filtration, by magnetic means, or by thermal decomposition
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B3/00—Extraction of metal compounds from ores or concentrates by wet processes
    • C22B3/20—Treatment or purification of solutions, e.g. obtained by leaching
    • C22B3/22—Treatment or purification of solutions, e.g. obtained by leaching by physical processes, e.g. by filtration, by magnetic means, or by thermal decomposition
    • C22B3/24—Treatment or purification of solutions, e.g. obtained by leaching by physical processes, e.g. by filtration, by magnetic means, or by thermal decomposition by adsorption on solid substances, e.g. by extraction with solid resins
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M8/00—Fuel cells; Manufacture thereof
    • H01M8/18—Regenerative fuel cells, e.g. redox flow batteries or secondary fuel cells
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B82—NANOTECHNOLOGY
    • B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
    • B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F1/00—Treatment of water, waste water, or sewage
    • C02F1/46—Treatment of water, waste water, or sewage by electrochemical methods
    • C02F1/469—Treatment of water, waste water, or sewage by electrochemical methods by electrochemical separation, e.g. by electro-osmosis, electrodialysis, electrophoresis
    • C02F1/4691—Capacitive deionisation
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/007—Contaminated open waterways, rivers, lakes or ponds
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/06—Contaminated groundwater or leachate
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/08—Seawater, e.g. for desalination
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2103/00—Nature of the water, waste water, sewage or sludge to be treated
    • C02F2103/10—Nature of the water, waste water, sewage or sludge to be treated from quarries or from mining activities
    • C—CHEMISTRY; METALLURGY
    • C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
    • C02F2201/00—Apparatus for treatment of water, waste water or sewage
    • C02F2201/46—Apparatus for electrochemical processes
    • C02F2201/461—Electrolysis apparatus
    • C02F2201/46105—Details relating to the electrolytic devices
    • C02F2201/46115—Electrolytic cell with membranes or diaphragms

Definitions

  • the disclosed subject matter relates to electrochemical ion pumping devices and methods of use thereof.
  • FIG. 1 Description of “rocking chair” electrosorption for desalination with a “batch-mode”: In the first half cycle (upper left), all channels are filled with the feed water. Electrode “b” is the cathode and electrodes “a” and “c” are the anodes. Cations are pulled into electrode “a” from the two channels it contacts, whereas the anions migrate across the anion exchange membrane (AEM) to maintain charge neutrality in these two channels. To maintain the charge neutrality of the channels on the other side of the anion exchange membrane, cations are discharged from electrodes “a” and “c” to neutralize the migrating anions.
  • AEM anion exchange membrane
  • Electrode “b” is saturated (either fully or partially) and electrodes “a” and “c” are regenerated (either fully or partially). The diluate and brine will be drained from the system and the channels will then be refilled with the feed solution. Electrode “b” is switched to become the anode and electrodes “a” and “c” are switched to become the cathodes, which marks the beginning of the second half cycle (bottom right).
  • electrode “b” is fully or partially regenerated and electrodes “a” and “c” are fully or partially saturated.
  • the channels with brine and diluate are then drained again, refilled with feed water, and the polarity of the voltages is switched to start the next cycle.
  • Electrodes “a” and “b” are the anode and cathode of circuit N, respectively. Whereas electrode “c” is the anode of circuit N+2 (the cathode of circuit N+2 is not shown).
  • cations are discharged from the anode to the brine stream and adsorbed to the cathode from the diluate stream.
  • Anions migrate across the anion exchange membrane from the diluate stream to the brine stream to maintain charge neutrality in both channels.
  • electrode “a” switches from the anode of circuit N to the cathode of circuit N-l (anode of circuit N-l is not shown)
  • electrode “b” switches from the cathode of circuit N to the anode of circuit N+l
  • electrode “c” switches from the anode of circuit N+2 to the cathode of circuit N+l .
  • Cation and anion transport in the second half cycle is similar to that in the first half cycle, except that they occur in a different cell pairs (and circuits).
  • FIG. 3 Description of CEIP with a multi-cell stack.
  • A the terminal anode and odd-numbered circuits are active.
  • B the terminal cathode and even-numbered circuits are active.
  • Electrodes “a” and “b” are the anode and cathode of circuit N, respectively. Whereas electrode “c” is the anode of circuit N+2 (the cathode of circuit N+2 is not shown).
  • Li + ions are discharged from the anode to the receiving solution (which becomes the Li-rich solution) and adsorbed to the cathode from the feed solution (which becomes the Li-lean solution. Anions migrate across the anion exchange membrane from the feed solution to the receiving solution to maintain charge neutrality in both channels.
  • electrode “a” switches from the anode of circuit N to the cathode of circuit N-l (anode of circuit N-l is not shown)
  • electrode “b” switches from the cathode of circuit N to the anode of circuit N+l
  • electrode “c” switches from the anode of circuit N+2 to the cathode of circuit N+L Li + ion and anion transport in the second half cycle is similar to that in the first half cycle, except that they occur in a different cell pairs (and circuits).
  • the circuit switch is performed again to perform the next cycle of ion pumping.
  • the active ion pumping occurs in circuits N and N+2 in the first half cycle, and in circuits N-l and N+l in the 2 nd half cycle.
  • Electrodes “a” and “b” are the anode and cathode of circuit N, respectively. Whereas electrode “c” and “d” are the anode and cathode of circuit N+2, respectively. In each circuit, cations adsorb onto the cathode and anions adsorb onto the anode, thereby desalinating the streams between “a” and “b” and between “c” and “d”.
  • FIG. 1 Schematic of an electrode to be used in CEIP.
  • Figure 8 Schematic illustration of how an electrode can be fabricated.
  • Figure 9 Illustration of a full cycle extracting Li + from the feed solution and enriching the ions in the receiving solution.
  • FIG. 10 Design of a Li-selective electrode comprising four major components: Li- intercalation material, carbon black (for improving conductivity), a conductive mesh current collector, and anion exchange polymer (AEP) filling the pores between the other three components.
  • Li- intercalation material Li- intercalation material
  • carbon black for improving conductivity
  • a conductive mesh current collector a conductive mesh current collector
  • AEP anion exchange polymer
  • FIG. 11 Design of a Li-selective electrode comprising four major components: Li- intercalation material, carbon black (for improving conductivity), a conductive mesh current collector, and anion exchange polymer (AEP) filling the pores between the other three components.
  • Li- intercalation material Li- intercalation material
  • carbon black for improving conductivity
  • a conductive mesh current collector a conductive mesh current collector
  • AEP anion exchange polymer
  • FIG. 12 Illustration of a full cycle for desalination using SCEIP.
  • the cathode in each circuit temporally uptakes cations from the diluate stream and discharges to the adjacent brine stream when it is used as the anode in the next cycle
  • Figure 14a- Figure 14f Working principle and proof-of-concept for electrochemical ion pump (EIP).
  • Figure 14a Working principle of conventional electro- sorption (ES) with solution- switch.
  • Figure 14b Working principle of EIP with circuit-switch.
  • the statistics of the half-cycle time for conventional electro- sorption are based on literature data as summarized in Table 1.
  • Figure 14c System design for asymmetric EIP (a-EIP) showing two consecutive circuits.
  • Figure 14d System design for symmetric EIP (s-EIP) showing two consecutive circuits. Both Figure 14c and Figure 14d show only part of a stack, whereas a full stack should include two terminal electrodes and possibly more circuits.
  • FIG 14e Photographic image and schematic of a complete s-EIP stack with a single cation electrode.
  • Figure 14f Performance of an s-EIP operated using a constant current density of 10 A nr 2 and a half-cycle time of 2 s.
  • a NaCl solution of 100 mM and a volume of 20 mL was used as the initial feed solution in both the diluate and brine channels.
  • the top graph shows the applied current waveform.
  • the middle graph presents the average voltages and current efficiencies of the charging and discharge half-cycles. The average voltage is calculated based on instant voltage (inset).
  • the bottom graph shows the change in concentration of the diluate and the brine. The diluate concentration steadily decreased as ions were transfer to the brine over the 950 min s-EIP experiment.
  • Figure 15a- Figure 15d Design, fabrication, and properties of cation adsorption electrodes (CE).
  • Figure 15a Illustration of cation electrode requirements and design.
  • the fundamental requirements include (i) fast ion transport, (ii) high electrical conductivity, and (iii) minimal water permeation.
  • the general design for a cation electrode meeting such requirements is a percolated activated carbon network connected to a current collector and filled with cation exchange polymer.
  • Figure 15b cation electrode fabrication strategy: the cation electrode was fabricated by preparing a composite film with a current collector embedded in a paste activated carbon particles and cation exchange polymer followed solvent evaporation (60 °C for 12 h) and hot-press (140 °C and 4000 psi) to form a water- impermeable dense film.
  • the cation electrode was encapsulated with a frame of waterproof tape for assembly into an EIP stack.
  • Figure 15c, Figure 15d Focused-ion beam scanning electron microscopy images with energy dispersive spectroscopy mapping, as well as photographic images of the electrodes (Figure 15c) before and ( Figure 15d) after hot-press.
  • Figure 16a- Figure 16f Behavior of a single-electrode s-EIP cell Ion flux and current efficiency at different current densities (6.25, 12.5, 50, and 125 A nr 2 ).
  • Figure 16b Average circuit voltage of the s-EIP cell (blue data points) and contribution to the circuit voltage from desalination (red data points) at different current densities, with the later obtained by subtracting the average circuit voltage and the cell voltage of an electrolytic cell. The half-cycle time was 5 s for results shown in both Figure 16a and Figure 16b.
  • Figure 16c Potential distribution across different components of an active circuit in the charging (left) and discharge (right) half-cycles of an s-EIP process.
  • Figure 16d Temporal change of diluate and brine concentrations for an s-EIP process (50 A nr 2 ) with a short half-cycle time of 5s (left) and a long half-cycle time of 500s (right).
  • the gray datapoints represent concentrations of the respective solutions when the solutions were not part of an active circuit.
  • Figure 16e Representative time profiles of circuit voltage for charging and discharge half-cycles in an s- EIP process (50 A nr 2 ) with different half-cycle times (0.5, 5, 50, and 500s).
  • Figure 16f Representative time profiles of cation electrode potential (vs. Ag/AgCl reference electrode) measured using 50 A nr 2 with different half-cycle times (0.5, 5, 50, and 500s) ( Figure 26).
  • Figure 17a- Figure 17k System design, behavior, and desalination performance of multi-electrode s-EIP stacks.
  • Figure 17a Photographic images of a 5-electrode s-EIP stack. The effective area for each cation electrode is 8 cm 2 .
  • Figure 17b Schematic of active circuit distribution in a full charging/discharge cycle for a 5-electrode s-EIP.
  • Figure 17g Illustration of charge transfer mechanisms (electrolysis vs.
  • Figure 17i Illustration of charge transfer mechanisms across an s-EIP stack with constant current operation and many cation electrodes.
  • Figure 17j Comparison of performance in terms SECi and ion flux between s-EIP and various film electrode-based capacitive deionization (CDI) processes tested for desalination with a similar feed salinity (details can be found in Figure 30a- Figure 30b, Table 2).
  • CDI film electrode-based capacitive deionization
  • Figure 17k Comparison of performance in terms of SECi and ion flux between s-EIP operated with constant current densities (8.1, 15, and 25 A nr 2 ) and constant circuit voltages (0.4, 0.8, and 1.2 V).
  • a process with a lower SECi and a high ion flux i.e., toward the bottom right of the SECi vs. ion flux plot
  • Results in this figure were obtained from experiments using a half-cycle time of 5 s, a feed concentration of 100 mM (NaCl) and a solution volume of 20 mL for both diluate and brine.
  • Figure 18a- Figure 18b Solution-switch in conventional electro-sorption.
  • Figure 18a Schematics of a conventional electro- sorption half-cell, which comprises the flow channel and the carbon electrode with macropores and micropores.
  • the top schematic in Figure 18a splits the electro- sorption half-cell into three visually distinct domains for clearer representation of concentrations, even though the macropores and micropores should co-exist in a macroscopic domain as indicated by the bottom schematic in Figure 18a.
  • Figure 18b Semi-quantitative profiles of salt/ion concentration for different stages in a full charging/discharge cycle.
  • C b , and C d represent the salt concentrations of the feed, brine, and diluate streams, respectively, whereas C mi toi is the total ion concentration in the micropores.
  • the concentration arrow is only semi-quantitative and not to scale.
  • FIG. 19 A typical full cycle of conventional electro-sorption (ES).
  • the feed solution/diluate recirculates between the electro-sorption cell and the diluate tank.
  • no ion is stored in the electrode micropores.
  • the feed solution is continually cycled between the external tank and the electrosorption cell.
  • ions in the feed solution are gradually adsorbed by the electrodes.
  • the electrodes reach saturation at a certain applied voltage.
  • the diluate stream within the electro- sorption cell is replaced by the receiving solution (brine) and the direction of the circuit is reversed.
  • the discharge operation ends.
  • the electrode capacity reverts to its initial state, ready for the subsequent adsorption cycles.
  • Figure 20a- Figure 20c Operation and desalination performance of a-EIP.
  • Figure 20a Working principle of asymmetrical electrochemical ion pump (a-EIP) with a pair of anion electrode (AE) and cation electrode (CE).
  • Figure 20b Performance of an s-EIP operated using a constant current density of 10 A m' 2 and a half-cycle time of 2 s.
  • a NaCl solution of 100 mM with a volume of 20 mL was used as the initial feed solution in both the feed (diluate) and brine channels.
  • the top graph shows voltages of different circuits.
  • the middle graph shows the current efficiency of the charging half-cycles.
  • the bottom graph shows the change in concentration of the diluate and the brine in >800 min s-EIP experiment.
  • Figure 20c Performance of s-EIP with constant current operation.
  • Figure 21a- Figure 21f s-EIP operated with constant voltage operation.
  • Figure 21a Circuit voltage waveform (2V) over multiple charging/discharge cycles (half-cycle time: 2s).
  • Figure 21b current density over multiple charging/discharge cycles.
  • Figure 21c Figure 2 Id, the same data as Figure 21a and Figure 21b but for a much longer operation time.
  • Figure 21e Changes in the concentrations of the diluate, the brine, and electrolyte.
  • Figure 21f average current efficiency over long-term operation.
  • Figure 22 Ion diffusion across electrode and IEM films.
  • Concentrations of the diluate and brine in experiments with spontaneous ion diffusion across commercial cation exchange membrane (CEM), cation electrode (CE), and conventional electro-sorption electrode without ion exchange polymer filler were used as the initial feed solution in the brine channels. 20 mL of DI water was used as the feed solution in the diluate channel.
  • the conventional electro- sorption electrode was fabricated using a blend comprising 80 wt% activated carbon (AC) and 20 wt% polyvinylidene fluoride (PVDF) without hot-pressing.
  • Figure 23a- Figure 23b Electrochemical test of cation electrode before and after hot- press.
  • Figure 23a Cyclic voltammogram results for cation electrodes with and without hot- press. The scan rate was 1 mV s' 1 .
  • Figure 23b Nyquist plot for cation electrodes with and without hot-press from electro-impedance spectroscopy (right), highlighting the importance of hot-press to reduce ohmic resistances of the cation electrode.
  • Figure 24a- Figure 24b Energy consumption of s-EIP.
  • Figure 24a Breakdown of energy consumed in s-EIP: desalination and electrolysis.
  • OER oxygen evolution reaction
  • AEM anion exchange membrane
  • HER hydrogen evolution reaction
  • FIG 24b Electrolytic cell for measuring the contribution from water electrolysis to circuit voltage.
  • Each half-cell comprises one terminal electrode, one solution chamber, and half of an anion exchange membrane.
  • Figure 25 Breakdown of voltage drop from electrode to solution.
  • the solid curves represent the overall potential in the bulk solution and the electrode.
  • the external resistance is related to the electron transfer through the wires, carbon matrix, and across the interface between current collector and carbon.
  • (p s represents the potential drop over the electrical double layer (Stern and Donnan).
  • Excess potential is the driving force for the ions to transport across the electrode in a finite rate.
  • FIG 26 Schematic of an electrochemical cell for measuring CE potential.
  • the two electrical relays control the circuit switching.
  • the working electrode serves as the cathode, with the CE on the left monitoring the electrode potential.
  • the working electrode functions as the anode, with the reference electrode on the right monitoring the electrode potential.
  • the reference electrodes are Ag/AgCl electrodes.
  • Figure 27a- Figure 27c Charge of solution pH and current efficiency under different current densities.
  • Figure 27a, Figure 27b Solution pH of diluate and brine under (Figure 27a) different current densities (6.25, 12.5, 50, and 125 A nr 2 ) and (Figure 27b) different halfcycle times (0.5, 5, 50, and 500 s).
  • Figure 27c Impact of half-cycle time on current efficiency.
  • FIG 28 Multi-electrode s-EIP with four cation electrodes: One half-cycle has three active circuits (top) while the other half-cycle has two active circuits (bottom). This differs from a multi-electrode s-EIP with odd number of electrodes (e.g., Figure 17b) where both half-cycles have the same number of electrodes.
  • Figure 29 pH of diluate and brine streams after 80 min in constant current vs. constant voltage mode. Substantial change of pH was observed in constant voltage mode to electrolysis. Specifically, OH' was generated in the diluate stream (thus pH increase) when the CE acted as a cathode, whereas H + was generated in the brine stream (thus pH decrease) when the CE acted as the anode.
  • Figure 30a- Figure 30b Specific energy consumption of multi-electrode s-EIP.
  • Figure 30b SECi as a function of number of cation electrodes for constant current and constant voltage modes. The red dashed line represents the SECi for desalination in for constant current mode (8.1 A m' 2 ) as obtained by subtracting the contribution from electrolysis at terminal electrodes from the measured overall SECi.
  • Figure 31 Performance comparison between s-EIP and conventional electro-sorption. This figure is a replicate of Figure 17k with additional labels for data points from literature. Squares, circles and triangles represent CDI, MCDI and R-CDI, respectively. The important results and parameters for these data points, along with their references, are listed in Table 2.
  • Figure 32a- Figure 32c Components and structures of EIP cells.
  • Figure 32a The components of an s-EIP cell.
  • Figure 32b The structure of the simplest s-EIP cell.
  • Figure 32c The structure of the simplest a-EIP cell.
  • the dimensions of the components are as follows: 1) End plate: PTFE, 100 x 100 mm x 10 mm; 2) Silicon mat: 60 x 60 mm x 2 mm; 3) Terminal electrode: Graphite paper, 60 x 60 mm x 3 mm; 4) Spacer: External dimensions 60 x 60 mm, with a central circular area of 40 mm diameter, thickness 1 mm; 5) Anion exchange membrane: 60 x 60 mm; 6) Working electrode: external dimension 60 x 60 mm, effective electrode area 8 cm 2 .
  • FIG 33 An example terminal electrode-free (e.g., circular) asymmetric electrochemical ion pump (EIP).
  • EIP electrochemical ion pump
  • FIG 34 An example terminal electrode-free (e.g., circular) symmetric electrochemical ion pump (EIP).
  • EIP electrochemical ion pump
  • Ranges can be expressed herein as from “about” one particular value, and/or to “about” another particular value. By “about” is meant within 5% of the value, e.g., within 4, 3, 2, or 1% of the value. When such a range is expressed, another aspect includes from the one particular value and/or to the other particular value. Similarly, when values are expressed as approximations, by use of the antecedent “about,” it will be understood that the particular value forms another aspect. It will be further understood that the endpoints of each of the ranges are significant both in relation to the other endpoint, and independently of the other endpoint.
  • Average generally refers to the statistical mean value.
  • substantially is meant within 5%, e.g., within 4%, 3%, 2%, or 1%.
  • references in the specification and concluding claims to parts by weight of a particular element or component in a composition denotes the weight relationship between the element or component and any other elements or components in the composition or article for which a part by weight is expressed.
  • X and Y are present at a weight ratio of 2:5, and are present in such ratio regardless of whether additional components are contained in the compound.
  • a weight percent (wt. %) of a component is based on the total weight of the formulation or composition in which the component is included.
  • A, B, C, or combinations thereof refers to all permutations and combinations of the listed items preceding the term.
  • “A, B, C, or combinations thereof’ is intended to include at least one of: A, B, C, AB, AC, BC, or ABC, and if order is important in a particular context, also BA, CA, CB, CBA, BCA, ACB, BAC, or CAB.
  • expressly included are combinations that contain repeats of one or more item or term, such as BB, AAA, AB, BBC, AAABCCCC, CBBAAA, CAB ABB, and so forth.
  • the skilled artisan will understand that typically there is no limit on the number of items or terms in any combination, unless otherwise apparent from the context.
  • Described herein are devices and methods of use thereof.
  • disclosed herein are electrochemical ion pumping devices and methods of use thereof.
  • each charging circuit comprises an anion electrode, a cation electrode, and a feed solution, the feed solution being sandwiched between and in electrochemical contact with the anion electrode and the cation electrode.
  • each discharging circuit comprises a cation electrode, an anion electrode, and a receiving solution, the receiving solution being sandwiched between and in electrochemical contact with the cation electrode and the anion electrode.
  • each pair of charging and discharging circuits further comprises a first electrical relay switch and a second electrical relay switch.
  • Each charging circuit and discharging circuit is fluidly independent.
  • each cation electrode is configured to adsorb and/or intercalate a target ion (e.g., a target cation).
  • each feed solution can be the same or different.
  • each feed solution comprises the target ion at an initial concentration.
  • each receiving solution comprises a counterion for the target ion. In some examples, each receiving solution comprises the target ion at a preliminary concentration.
  • the anion electrode and the cation electrode of each charging circuit are electrically connected to each other and a voltage source via the first and second electrical relay switches, and at least a portion of the target ion concentration is depleted from each of the feed solutions by being adsorbed and/or intercalated into the cation electrodes, such that the concentration of the target ion in the feed solutions decreases relative to the initial concentration.
  • the cation electrode and the anion electrode of each discharging circuit are electrically connected to each other and the voltage source via the first and second electrical relay switches, at least a portion of the target ion adsorbed and/or intercalated in the cation electrode is released into the receiving solution, such that the concentration of the target ion in the receiving solution increases relative to the preliminary concentration.
  • each circuit comprises a receiving channel and a feed channel, the receiving channel being fluidly independent from the feed channel.
  • the receiving channel is defined by a first cation electrode and an anion exchange membrane, the receiving channel containing a receiving solution, such that the receiving solution is sandwiched between and in electrochemical contact with the first cation electrode and the anion exchange membrane.
  • the feed channel is defined by the anion exchange membrane and a second cation electrode, the feed channel containing a feed solution, the feed solution being sandwiched between and in electrochemical contact with the anion exchange membrane and the second cation electrode.
  • each pair of circuits further comprises a first electrical relay switch and a second electrical relay switch.
  • each cation electrode is shared between two neighboring circuits, but is only connected to one circuit in every half cycle via the first and second electrical relay switches.
  • each cation electrode is configured to adsorb and/or intercalate a target ion (e.g., a target cation).
  • each feed solution can be the same or different.
  • each feed solution comprises the target ion at an initial concentration.
  • each receiving solution comprises a counterion for the target ion.
  • each receiving solution comprises the target ion at a preliminary concentration.
  • each cation electrode functions as the cathode of one circuit to adsorb the target ion from the feed solution in its charging half-cycle, and as the anode of another circuit to release the target ions to the receiving solution in its discharge half-cycle, the switch of a cation electrode between two adjacent circuits is achieved by electrical relay switches; such that when a circuit is operated in a charging mode, then the target ions from the feed solution contacting one side of the cation electrode are electrochemically absorbed by said side of the cation electrode, and when the circuit is operated in discharging mode, then the target ions are released from the cation electrode into the receiving solution contacting the opposite side of the cation electrode.
  • the first cation electrode and the second cation electrode are electrically connected to each other and a voltage source via the first and second electrical relay switches, the voltage source being configured to apply a voltage to the first and second cation electrodes such that at least a portion of the target ion concentration is depleted from each of the feed solutions by being adsorbed and/or intercalated into the cation electrode, such that the concentration of the target ion in the feed solutions decreases relative to the initial concentration.
  • the first cation electrode and the second cation electrode are electrically connected to each other and a voltage source via the first and second electrical relay switches, the voltage source being configured to apply a voltage to the first and second cation electrodes such that at least a portion of the target ion adsorbed and/or intercalated in the cation electrode is released into the receiving solution, such that the concentration of the target ion in the receiving solution increases relative to the preliminary concentration.
  • the voltage source being configured to apply a voltage to the first and second cation electrodes such that at least a portion of the target ion adsorbed and/or intercalated in the cation electrode is released into the receiving solution, such that the concentration of the target ion in the receiving solution increases relative to the preliminary concentration.
  • half of the circuits or electrodes in the device can be charging and the other half of the circuits or electrodes in the device are discharging.
  • the target ion comprises a critical mineral.
  • critical minerals include, but are not limited to, aluminum, antimony, arsenic, barite, beryllium, bismuth, cerium, cesium, chromium, cobalt, copper, dysprosium, erbium, europium, gadolinium, gallium, germanium, graphite, hafnium, holmium, indium, iridium, lanthanum, lithium, lutetium, magnesium, manganese, neodymium, nickel, niobium, palladium, platinum, praseodymium, rhodium, rubidium, ruthenium, samarium, scandium, silicon, tantalum, tellurium, terbium, thulium, tin, titanium, tungsten, vanadium, ytterbium, yttrium, zinc, and zirconium.
  • the target ion comprises a metal, such as an alkaline metal, a transition metal, a rare earth metal, or a combination thereof.
  • the target ion comprises sodium, lithium, nickel, copper, cobalt, or a combination thereof. In some examples, the target ion comprises sodium, lithium, or a combination thereof.
  • each charging circuit comprises a cation electrode, an anion electrode, and a feed solution, the feed solution being sandwiched between and in electrochemical contact with the anion electrode and the cation electrode.
  • each discharging circuit comprises an anion electrode, a cation electrode, and a receiving solution, the receiving solution being sandwiched between and in electrochemical contact with the cation electrode and the anion electrode.
  • each pair of charging and discharging circuits includes three total electrodes.
  • each pair of charging and discharging circuits further comprising a first electrical relay switch and a second electrical relay switch.
  • Each charging circuit and discharging circuit are fluidly independent.
  • each anion electrode is configured to adsorb and/or intercalate a target ion (e.g., a target anion).
  • each feed solution can be the same or different.
  • each feed solution can comprise the target ion at an initial concentration.
  • each receiving solution comprises a counterion for the target ion. In some examples, each receiving solution comprises the target ion at a preliminary concentration.
  • the anion electrode and the cation electrode of each charging circuit are electrically connected to each other and a voltage source via the first and second electrical relay switches, and at least a portion of the target ion concentration is depleted from each of the feed solutions by being adsorbed and/or intercalated into the anion electrodes, such that the concentration of the target ion in the feed solutions decreases relative to the initial concentration.
  • the cation electrode and the anion electrode of each discharging circuit are electrically connected to each other and the voltage source via the first and second electrical relay switches, at least a portion of the target ion adsorbed and/or intercalated in the anion electrode is released into the receiving solution, such that the concentration of the target ion in the receiving solution increases relative to the preliminary concentration.
  • each circuit comprises a receiving channel and a feed channel, the receiving channel being fluidly independent from the feed channel.
  • the receiving channel is defined by a first anion electrode and a cation exchange membrane, the receiving channel containing a receiving solution, such that the receiving solution is sandwiched between and in electrochemical contact with the first anion electrode and the cation exchange membrane.
  • the feed channel is defined by the cation exchange membrane and a second anion electrode, the feed channel containing a feed solution, the feed solution being sandwiched between and in electrochemical contact with the cation exchange membrane and the second anion electrode.
  • each pair of circuits further comprises a first electrical relay switch and a second electrical relay switch.
  • each anion electrode is shared between two neighboring circuits, but is only connected to one circuit in every half cycle via the first and second electrical relay switches.
  • each anion electrode being configured to adsorb and/or intercalate a target ion (e.g., a target anion).
  • each feed solution can be the same or different.
  • each feed solution comprises the target ion at an initial concentration.
  • each receiving solution comprises a counterion for the target ion.
  • each receiving solution comprises the target ion at a preliminary concentration.
  • each anion electrode functions as the cathode of one circuit to adsorb the target ion from the feed solution in its charging half-cycle, and as the anode of another circuit to release the target ions to the receiving solution in its discharge half-cycle, the switch of an anion electrode between two adjacent circuits is achieved by electrical relay switches; such that when a circuit is operated in a charging mode, then the target ions from the feed solution contacting one side of the anion electrode are electrochemically absorbed by said side of the anion electrode, and when the circuit is operated in discharging mode, then the target ions are released from the cation electrode into the receiving solution contacting the opposite side of the anion electrode.
  • the first anion electrode and the second anion electrode are electrically connected to each other and a voltage source via the first and second electrical relay switches, the voltage source being configured to apply a voltage to the first and second anion electrodes such that at least a portion of the target ion concentration is depleted from each of the feed solutions by being adsorbed and/or intercalated into the anion electrode, such that the concentration of the target ion in the feed solutions decreases relative to the initial concentration.
  • the first anion electrode and the second anion electrode are electrically connected to each other and a voltage source via the first and second electrical relay switches, the voltage source being configured to apply a voltage to the first and second anion electrodes such that at least a portion of the target ion adsorbed and/or intercalated in the anion electrode is released into the receiving solution, such that the concentration of the target ion in the receiving solution increases relative to the preliminary concentration.
  • the voltage source being configured to apply a voltage to the first and second anion electrodes such that at least a portion of the target ion adsorbed and/or intercalated in the anion electrode is released into the receiving solution, such that the concentration of the target ion in the receiving solution increases relative to the preliminary concentration.
  • half of the circuits or electrodes in the device can be charging and the other half of the circuits or electrodes in the device are discharging.
  • each of the feed solutions and/or receiving solutions further comprises a solvent, such as water (e.g., each of the feed solutions and/or receiving solutions is an aqueous solution).
  • a solvent such as water
  • the feed solution is derived from natural sources or a waste streams.
  • the feed solution comprises brackish water, salt lake brine, seawater, geothermal brine, oil and/or gas produced water, mining wastewater, leaching solution in battery recovery, or a combination thereof.
  • the feed solution comprises a salt solution, produced water (e.g., from mining, fracking, oil recovery), brine, or a combination thereof.
  • the feed solution comprises brine resulting from the power industry, chemical industry, food industry, oil and gas industry (e.g., hydraulic fracturing), desalination industry (e.g., inland brackish water desalination), mining industry, or a combination thereof.
  • the feed solution can comprise any type of water, treated or untreated.
  • the feed solution can comprise hard water, hard brine, sea water, brackish water, fresh water, flowback or produced water, wastewater (e.g., reclaimed or recycled), river water, lake or pond water, aquifer water, brine (e.g., reservoir or synthetic brine), slickwater, or a combination thereof.
  • the feed solution can comprise hard water, hard brine, sea water, brackish water, flowback or produced water, wastewater (e.g., reclaimed or recycled), brine (e.g., reservoir or synthetic brine), slickwater, or a combination thereof.
  • the feed solution can comprise wastewater, such as industrial wastewater and/or wastewater from unconventional energy production.
  • the feed solution can comprise wastewater from gas and/or oil production from a subterranean formation (e.g., unconventional formation, conventional formation).
  • the feed solution can comprise wastewater from gas and/or oil production from an unconventional subterranean formation (e.g., shale formation).
  • the feed solution comprises unconventional oil wastewater (e.g., shale oil wastewater), unconventional gas wastewater (e.g., shale gas wastewater), conventional oil wastewater, conventional gas wastewater, or a combination thereof.
  • the feed solution comprises mining wastewater, flue gas desulfurization wastewater (this is from coal power plant), chemical industry wastewater, or a combination thereof.
  • the plurality of circuits are stacked or arranged linearly, and the device further comprising one or more terminal electrodes (e.g., two or more terminal electrodes).
  • the plurality of circuits are stacked or arranged circularly (e.g., to form at least part of a circle).
  • the cation and/or anion electrodes enable fast transport of the target ion from the feed solution to the receiving solution, have minimal macropores to avoid direct mixing between the feed solution and the receiving solution, are electrically conductive to minimize resistive energy loss, or a combination thereof.
  • the methods can comprise separating the target ion from the feed solution.
  • the method comprises critical mineral extraction, for example from natural sources or recovery from waste streams. In some examples, the method comprises desalination.
  • the method comprises the electrochemical adsorption of the target ions from the feed solution contacting one side of the cation or anion electrode, followed by the subsequent release of the target ions to the receiving solution contacting the opposite side of the cation or anion electrode.
  • the method is continuous or semi-continuous.
  • the charge/discharge half cycles have a cycle time of 0.1 seconds or more (e.g., 0.25 seconds or more, 0.5 seconds or more, 0.75 seconds or more, 1 seconds or more, 1.25 seconds or more, 1.5 seconds or more, 1.75 seconds or more, 2 seconds or more, 2.5 seconds or more, 3 seconds or more, 3.5 seconds or more, 4 seconds or more, 4.5 seconds or more, 5 seconds or more, 6 seconds or more, 7 seconds or more, 8 seconds or more, 9 seconds or more, 10 seconds or more, 15 seconds or more, 20 seconds or more, 25 seconds or more, 30 seconds or more, 35 seconds or more, 40 seconds or more, 45 seconds or more, 50 seconds or more, 55 seconds or more, 1 minute or more, 1.25 minutes or more, 1.5 minutes or more, 1.75 minutes or more, 2 minutes or more, 2.5 minutes or more, 3 minutes or more, 3.5 minutes or more, 4 minutes or more, 4.5 minutes or more, 5 minutes or more, 6 minutes or more, 7 minutes or more, 8 minutes or more, 9 minutes or more,
  • the charge/discharge half cycles have a cycle time of 100 minutes or less (e.g., 90 minutes or less, 80 minutes or less, 70 minutes or less, 60 minutes or less, 50 minutes or less, 45 minutes or less, 40 minutes or less, 35 minutes or less, 30 minutes or less, 25 minutes or less, 20 minutes or less, 15 minutes or less, 10 minutes or less, 9 minutes or less, 8 minutes or less, 7 minutes or less, 6 minutes or less, 5 minutes or less, 4.5 minutes or less, 4 minutes or less, 3.5 minutes or less, 3 minutes or less, 2.5 minutes or less, 2 minutes or less, 1.75 minutes or less, 1.5 minutes or less, 1.25 1 minute or less, 55 seconds or less, 50 seconds or less, 45 seconds or less, 40 seconds or less, 35 seconds or less, 30 seconds or less, 25 seconds or less, 20 seconds or less, 15 seconds or less, 10 seconds or less, 9 seconds or less, 8 seconds or less, 7 seconds or less, 6 seconds or less, 5 seconds or less, 4.5 seconds or less, 4 seconds or less, 100 minutes or less
  • the cycle time can range from any of the minimum values described above to any of the maximum values described above.
  • the charge/discharge half cycles have a cycle time of from 0.1 seconds to 100 minutes (e.g., from 0.1 second to 50 minutes, from 50 minutes to 100 minutes, from 0.1 seconds to 1 second, from 1 second to 1 minute, from 1 minute to 10 minutes, from 10 minutes to 100 minutes, from 0.1 seconds to 60 minutes, from 0.1 seconds to 30 minutes, from 0.1 seconds to 15 minutes, from 0.1 seconds to 10 minutes, from 0.1 seconds to 5 minutes, or from 0.1 seconds to 1 minute).
  • the charge/discharge half cycles have a cycle time of from 0.1 seconds to 10 minutes.
  • the charge/discharge half cycles have a cycle time of from 0.1 seconds to 1 minute.
  • the charge/discharge half cycles are short.
  • Electrochemical adsorption (or electrosorption) of ions from aqueous solution such as brackish water, seawater, and brines has important applications for desalination and selective extraction of minerals and other valuable ions. Electrosorption works by temporarily storing the ions in the electrodes in the charging step and releasing these ions in the discharge step. Specifically, in the charging step, a voltage is applied to a pair of electrodes to adsorb the cations to the negative electrode and the anions to the positive electrode. In the discharge step, the applied voltage is changed to release the adsorbed ions from the electrodes.
  • Such a change can take different forms, e.g., the applied voltage can be reduced, set to zero (i.e., the electrodes are short-circuited), or reversed.
  • the target ions are removed from a batch (or stream) of the feed solution in the charging step and released to a separate batch (or stream) of solution, thereby achieving separation.
  • Electrode materials with these mechanisms have all been tested for desalination which does not require specificity in the removed ions. For selective ion extraction, however, intercalation and Faradaic mechanisms are more promising because the electrode materials can be selected or tailored to achieve selective adsorption of specific ions.
  • the “rocking chair” configuration typically uses symmetric electrodes that adsorb only cations (although anion adsorption electrodes may be developed). Most commonly, the electrodes used in such a configuration involve intercalation or Faradaic reaction mechanisms, even though activated carbon electrodes based on electrical double layer formation can also be used.
  • a voltage is applied to a pair of cation intercalation electrodes contacting two solution chambers separated by an anion exchange membrane (AEM).
  • AEM anion exchange membrane
  • the cations are removed from the solution in cathodic chamber via intercalation into the cathode and released from the anode into the solution of the anodic chamber, while the anions in the cathodic chamber transport through the anion exchange membrane to the anodic chamber.
  • the applied voltage is flipped once the cathode is charged to the desired level.
  • the streams exiting the cathodic and anodic chambers are the desalinated stream and brine streams, respectively.
  • the feedwater flows through the anodic chamber whereas the product stream receiving the cations released from the electrodes flows through the anodic chamber.
  • these systems have a major challenge, which is the switch of streams between the charging and discharge steps. While the switching of streams can be achieved using valve control, the finite time for the solution in the cell to be completely replaced by new solution undermines the system performance due to the mixing between the diluate and brine (in desalination) or between the feed solution and receiving solution (in selective ion extraction). In desalination, for instance, this effect of finite switching time prevents the diluate stream salinity to reach a new steady state even with constant current. In selective ion extraction, the mixing between the feed solution and receiving solution is the “contamination” of the receiving solution by other non-target ions in the feed solution.
  • One possible way to mitigate this challenge is to use electrodes with high adsorption capacity to minimize the switching time as compared to the charging and discharge time.
  • attaining a leapfrog in electrodes’ adsorption capacity over the state-of-the-art is very difficult.
  • CEIP continuous electrochemical ion pumping
  • the circuit is switched again to perform the next cycle of ion pumping.
  • the active ion pumping occurs in circuits N and N+2 in the first half cycle, and in circuits N-l and N+l in the 2 nd half cycle.
  • CEIP By switching circuits in CEIP instead of switching flows in “rocking chair” electrosorption, ion transport direction can always be maintained and the limitations due to solution mixing in flow switching can be circumvented.
  • the unique operation mode of CEIP also allows working with a very low saturation of level for the electrodes, which in theory should have benefits in both kinetics and energy consumption as adsorption will become more “challenging” as the electrodes become more saturated.
  • the circuit switching is controlled automatically by a logic board and the half cycle can be as short as Is or less and as long as needed.
  • the schematic in Figure 2 only shows one and half cells, but multiple cells can be stacked together to form a multi-cell stack (Figure 3).
  • the N-cell stack comprises N anion exchange membranes (AEM), N-l cation adsorption electrodes (CAE), N-l dilute channels, N-l brine channels, two terminal electrodes for electrolysis, and two terminal electrode channels containing electrolyte solutions.
  • AEM N anion exchange membranes
  • CAE N-l cation adsorption electrodes
  • N-l dilute channels N-l brine channels
  • two terminal electrodes for electrolysis two terminal electrodes for electrolysis
  • two terminal electrode channels containing electrolyte solutions In the 1 st half cycle (Figure 3, panel A), electrolysis occurs in the terminal anode to produce H + to neutralize the anions coming from the adjacent diluate channel, the terminal cathode is not connected.
  • porous carbon e.g., activated carbon, carbon black
  • the positively charged porous carbon is able to adsorb anions, when the negatively charged porous carbon at the cathode adsorbs cations.
  • the porous carbon of the cathode and anode are mixed on the outside of the cell and the porous electricity is regenerated.
  • a CEIP system can also function with a single-cell configuration ( Figure 4) which comprises one cation adsorption electrode, two anion exchange membranes, one brine stream, one diluate stream, two terminal electrodes, and two electrolyte streams contacting the terminal electrodes.
  • Figure 4 a single-cell configuration
  • a single-cell configuration which comprises one cation adsorption electrode, two anion exchange membranes, one brine stream, one diluate stream, two terminal electrodes, and two electrolyte streams contacting the terminal electrodes.
  • the CEIP process can also be applied for continuous and selective extraction and enrichment of target ions from a complex mixture, provided that the ion adsorption electrodes are selective to the target ions (e.g., critical minerals and materials).
  • target ions e.g., critical minerals and materials.
  • lithium (Li) extraction from a feed stream containing a complex mixture of other cations is used as an example.
  • the working principle is very much similar to what has been described for desalination in Figure 2, except that here the cation adsorption electrode is replaced with a Li-selective cation adsorption electrode which has a preferential adsorption/intercalation of Li + over other cations.
  • Each cell comprises two Li-selective cation adsorption electrode, an anion exchange membrane, one receiving solution which later becomes the Li-rich solution, and a feed solution that later becomes the Li-lean solution.
  • the receiving solution could be a solution of Li salt (without other metal cations)
  • the feed solution can be any solutions with Li, including but are not limited to, salt lake brine, geothermal brine, produced water, mining wastewater, leaching solution in battery recovery, and seawater.
  • the stacks for CEIP for Li extraction can be a multi-cell stack (similar to that in Figure 3) and single-cell stack (similar to that in Figure 4).
  • Selective CEIP can also be applied to extract and enrich other types of cations and anions, as long as the corresponding electrodes selective to those ions are available.
  • the anion exchange membrane in Figure 5 will be replaced by a cation exchange membrane (CEM).
  • the ion intercalation electrodes can also be replaced by activated carbon (AC) filled with ion exchange resins.
  • AC activated carbon
  • the cation intercalation electrodes can be replaced with activated carbon filled with cation exchange resins (to close up macropores); the anion intercalation electrodes can be replaced with activated carbon filled with anion exchange resins (to close up macropores).
  • both cation intercalation electrodes (or activated carbon filled with cation exchange resins) and anion interaction electrodes (or activated carbon filled anion exchange resins) can also be used at the same time without using any ion exchange membranes.
  • additional expansions include, but are not limited to: Cation exchange polymer plus activated carbon;
  • Cation intercalation material plus inorganic material e.g., aluminum, titanium and alloys
  • carbon electrode either using activated carbon with binder or activated carbon cloth
  • additional expansions include, but are not limited to:
  • Carbon electrode (either using activated carbon with binder or activated carbon cloth) with surface coated with an cation exchange polymer film.
  • the ion adsorption electrodes used in CEIP should have the following characteristics:
  • the macropores of the electrode are filled with an ion-exchange polymer (or other material); 2. using an ion exchange polymer to cover one side of the electrode, but the macropores of the electrode remain; 3. the electrode is prepared without macropores, which may be the case in intercalation electrodes used for lithium extraction.
  • Step 1 Mix and ball-mill (optional) active electrode materials (e.g., activated carbon, cation intercalation materials, anion interaction materials, or other types) with conductive additives (e.g., carbon black).
  • active electrode materials e.g., activated carbon, cation intercalation materials, anion interaction materials, or other types
  • conductive additives e.g., carbon black
  • the active electrode materials provide the capacity for ion storage, and the conductive additives increase the electrical conductivity of the electrodes.
  • the ball-milling will reduce the particle size and improve contact between active electrode materials and the conductive additive.
  • Step 2 Mix the powder mixture obtained from step 1 with a polymer solution.
  • the polymer can be anion exchange polymer (or positively charged polyelectrolyte), cation exchange polymer (or positively charged polyelectrolyte), a non-ionic polymer, or a combination of these polymers in a mixture or as stratified layers.
  • the resulting powder/polymer mixture is the electrode slurry.
  • Step 3 Cover a mesh, fibroid current collector (e.g., graphite, titanium) with the electrode slurry obtained from step 2 so that the current collected is fully or partially embedded in a film of the electrode slurry.
  • a mesh, fibroid current collector e.g., graphite, titanium
  • Step 4 Hot press the current collector-embedded film at high temperature and pressure to form the working film electrode.
  • CEIP can be used for desalination and selective separation to either remove or enrich specific ions using electrodes that can adsorb those ions with specificity.
  • electrodes that can adsorb those ions with specificity.
  • possible electrode materials can be inorganic particles comprising lithium, manganese, titanium, and oxygen (e.g., lithium manganese oxide, lithium titanium oxide, lithium titanium and manganese oxides). Other electrode materials can also be used.
  • solvent extraction and adsorption have major limitations such as high chemical usage and operational complexity due to non-continuous operation.
  • the use of organic solvents in solvent extraction and strong acids as the leaching solution in both processes poses significant occupational and environmental risks.
  • Solvent extraction and adsorbent-based extraction involve two distinct steps, including an extraction (or adsorption) step and a stripping (or leaching) step, which induces significant operational complexity.
  • Electro-sorption is a promising electrochemical method for extracting critical minerals. Take Li for example, electro- sorption using Li intercalation materials has been demonstrated to be a promising direction for Li extraction from a variety of brines.
  • Li intercalation electrodes such as manganese oxide (Z-M CL) and lithium iron phosphate (LiFePCh), have been used to selectively adsorb Li + from a complex mixture of other ions and then release to a receiving solution.
  • Electrodialysis also suffers from similar limitations such as the challenge for achieving a high Li-specific selectivity (other than monovalent-divalent selectivity) and the loss of selectivity at high ionic strength.
  • NF nanofiltration
  • ED electrodialysis
  • adsorption can typically achieve a much higher selectivity, and electro-sorption with intercalation electrodes thus also has the potential to become a highly selective Li extraction process.
  • electro-sorption based on intercalation-electrodes has advantages over nanofiltration or electrodialysis in achieving a high ion-specific selectivity, it is, to a certain extent, still a non-continuous process.
  • the operation of electro-sorption involves two distinct steps: the adsorption (or charging) step and the desorption (or discharge) step.
  • the non- continuous operation of a conventional electro- sorption process creates a major challenge when switching the solutions (or the flows) between the feed solution and the receiving solution (i.e., the product stream). The inevitable mixing between the two solutions can significantly undermine the selectivity and recovery of the target ions.
  • intercalation electrodes may capture the target ions with a high selectivity by storing them in the electrodes’ crystal lattice
  • competing ions are also stored in the “macropores” (i.e., pores between the particles of intercalation materials) and later released to the product stream, further compromising the selectivity.
  • the electro- sorption research community has been trying to develop electrodes with higher capacity, as achieving more adsorption in the charging step can reduce the detrimental impacts due to flow switch and discharge of competing ions from macropores.
  • Described herein is a technological platform to separate a critical mineral from aqueous solutions relevant to critical mineral extraction from natural sources or recovery from industrial waste streams.
  • This technological platform namely Selective and Continuous Electrochemical Ion Pump (SCEIP), an ion-selective electro- sorption process that can operate continuously without solution mixing and discharge of competing ions.
  • Solution mixing and discharge of competing ions which are unavoidable in conventional electrosorption with “flow switch”, are detrimental to both selectivity and energy efficiency of the critical mineral extraction process.
  • SCEIP is described with a focus on extracting lithium (Li) and nickel (Ni) which involve two fundamentally different mechanisms to achieve ion selectivity.
  • Li-selective version of SCEIP Selective and Continuous Electrochemical Lithium Pump (SCELiP) with the target application as Li-extraction from geothermal brine and produced water.
  • Ni-selective version of SCEIP, Selective and Continuous Electrochemical Lithium Pump, (SCENiP) with the target application as recovering Ni from spent solutions in electroplating industry (e.g., electroless and electrolytic baths).
  • a SCEIP stack comprises multiple cells with each cell having two ion-selective electrodes, an anion exchange membrane (AEM), one receiving solution which later becomes rich in the target ions, and a feed solution that later becomes lean in the target ions.
  • the receiving solution could be a pure solution containing only the target ions and their counter ions
  • the feed solution can be any solutions containing the target ions (e.g., geothermal brine, produced water, mining wastewater, leaching solution in battery recovery).
  • SCELiP is used as an example to describe the working principle of SCEIP, noting that the principle is the same for SCENiP and other metals except for the target ion species and the electrode design.
  • electrodes “a” and “b” are the anode and cathode of circuit N, respectively. Whereas electrode “c” is the anode of circuit N+2 (the cathode of circuit N+2 is not shown).
  • Li ions are discharged from the anode to the receiving solution (Li-rich solution) and adsorbed to the cathode from the feed solution. Anions migrate across the anion exchange membrane from the feed solution to the receiving solution to maintain charge neutrality in both channels.
  • electrode “a” switches from the anode of circuit N to the cathode of circuit N-l (anode of circuit N-l is not shown)
  • electrode “b” switches from the cathode of circuit N to the anode of circuit N+l
  • electrode “c” switches from the anode of circuit N+2 to the cathode of circuit N+L Li ions and anions’ transport in the second half cycle is similar to that in the first half cycle, except that they occur in different cells (and circuits).
  • the circuit is switched again to perform the next cycle of Li ion pumping.
  • the active ion pumping occurs in circuits N and N+2 in the first half cycle, and in circuits N-l and N+l in the 2nd half cycle.
  • a unique feature of SCELiP (as compared to conventional electro- sorption) is to use “circuit switch” to replace “flow switch”.
  • SCELiP replaces the more difficult and slower control of water flows with the easier and much faster control of the electron flows, which provides several key advantages.
  • the absence of “flow switch” in SCELiP eliminates mixing between the feed solution and the receiving solution as well as the discharge of impurity cations from the macropores of the electrodes to the receiving solution — both phenomena are detrimental to selectivity in conventional electro-sorption.
  • SCELiP With SCELiP, however, high-capacity electrodes are unnecessary because there is no “flow switch” or its detrimental impacts in the entire process. Instead of adsorbing as much as Li ions to the electrode in the charging halfcycle and then releasing them to the receiving solution as in conventional electro- sorption, SCELiP only needs to capture a small amount of Li ions in the electrode for a very brief time (i.e., short half cycle time) and then release them to the receiving solution.
  • SCELiP not require high-capacity electrodes, but a very short halfcycle time can be used and a very low saturation level of the electrodes can be maintained, which is another advantage of the SCELiP. It is well known in desalination theory that charging the electrodes to a high saturation level is unfavorable in both kinetics and energy consumption. In the case of selective ion removal, high saturation level may even compromise selectivity. Operating with a low saturation level is impractical for conventional electro- sorption due to the detrimental impacts of “flow switch” but is completely feasible and actually desirable in SCELiP. With all these advantages considered, SCELiP has a strong potential to become a continuous, high selective, energy-efficient, and operationally simple and robust process for electrochemical Li extraction.
  • the Li-selective electrode in SCELiP is a symmetric thin film made of Li-intercalation materials, carbon black (for improving conductivity), a conductive mesh as current collector, and positively charged anion exchange polymers (AEP) filling the macropores in the electrode ( Figure 10).
  • the anion exchange polymer fully or partially blocks the macropores to prevent diffusional crossover of ions other than Li, and its positively charge helps to exclude competing cations from entering the film during charging (the electrode).
  • Partial filling refers to the macropores of a very thin surface layer of electrode particles being filled. In addition, it is important to avoid the complete coverage of electrode particles by the anion exchange polymer, ensuring that the electrode particles remain exposed to the feed solution.
  • Li-selective electrode When the Li-selective electrode is used as the cathode, Li ions in the feed solution will be inserted in the exposed Li-intercalation materials.
  • the anion exchange resin does not fully cover the electrode surface, leaving the intercalation electrode material exposed to the solution. Other cations that cannot enter the crystal lattice of the intercalation materials will be rejected by the positive charge imparted by the anion exchange polymer.
  • Li-selective electrode is used as anode, Li ions stored in the intercalation electrode will be released to the receiving solution.
  • top layer is as described in the preceding paragraph but is very thin
  • support layer is a cation exchange membrane.
  • the conductive mesh only needs to contact the electrode materials, but not necessarily embedded in the film.
  • SCENiP Electrode Design For SCENiP selective extraction of Ni can be achieved using some 2D pseudocapacitor materials (intercalation materials) such as TiS2, MoS2.
  • intercalation materials such as TiS2, MoS2.
  • the electrodes are prepared in the same way as previously described for lithium intercalation material electrodes.
  • Ni selective electrodes for SCENiP can use other approach.
  • the Ni-selective electrode used in SCENiP is an asymmetric electrode integrating two functional layers ( Figure 11).
  • the base layer comprises a mixture of activated carbon (AC), carbon black, and cation exchange polymer (CEP).
  • a mesh current collector is used to apply the potential to the base layer.
  • the coating layer is a composite film made anion exchange polymer and a Ni-binding functional material (either polymer or inorganic particles) that forms a percolation network through the composite film.
  • Ni-selective electrode When the Ni-selective electrode is used as the cathode, Ni ions in the feed solution will transport along the percolation network through the coating layer and enter the activated carbon-containing base layer. Other cations not binding to the functional material will be rejected by the positive charge imparted by the anion exchange polymer and thus cannot enter the activated carbon electrode.
  • Ni-selective electrode When the Ni-selective electrode is used as anode, Ni ions stored in the activated carbon electrode will be released to the receiving solution. The anions cannot enter the activated carbon electrode due to the exclusion by the cation exchange polymer, which maintain a high current efficiency for Ni discharge process.
  • SCELiP and SCENiP are two of the many examples for SCEIP.
  • SCEIP can be applied to extract many other ions using both approach 1 where intercalation electrodes for a specific ion are used (SCELiP as an example) and approach 2 where a selective same-charge polymer coating embedded with specific ion-binding additive is used to impart selectivity.
  • Other ions that can be extracted using SCEIP include, but are not limited to, copper, cobalt, alkaline metals, transition metals, and rare earth metals.
  • SCEIP Proof of Concept of SCEIP in Desalination.
  • One major advantage of SCEIP is the unique way in which the charging and discharge is performed, not via switching the polarity in a circuit, but via switching the active circuits between adjacent half-cycles. This unique operation approach enables continuous separation and the elimination of flow switch, which improves separation performance, reduces operation complexity and the requirements on electrode capacity.
  • SCEIP can be pursued for the extraction of Li (SCELiP) and Ni (SCENiP)
  • the feasibility of this unique circuit switch approach was confirmed in a recent study on desalination using the system shown in Figure 12. The data for desalination is shown in Figure 13.
  • electrochemical ion pump powered by the mechanism of circuit-switch-induced ion shuttling, offers a highly scalable approach to overcome the limitations of solution- switch and achieve pseudo-continuous ion separation with unidirectional ion flux.
  • the feasibility EIP is demonstrated with symmetric and asymmetric configurations and a systematic investigation of symmetric EIP was performed with a single electrode and with multiple electrodes. Interesting system behaviors of multi-electrode EIP are unveiled that are critical to scaling up EIP for practical applications.
  • Salient performance enhancement of EIP vs. conventional electro-sorption is also shown with various types of configurations for brackish water desalination. Beside its exceptional scalability and performance, the ability of EIP to operate with ultrashort halfcycles with minimum capacitance has a strong potential to shift the paradigm for electrode design in a broad range of electrochemical separation applications.
  • Electro- sorption is an important class of electrochemical separation inspired by the mechanism of supercapacitor and battery for energy storage (Suss ME et al. Energy Environ. Sci. 2015, 8, 2296-2319; Biesheuvel P et al. arXiv preprint, 2017, arXiv: 1709.05925; Fleischmann S et al.
  • a general electro-sorption process comprises charging and discharge half-cycles (Porada S et al. Prog. Mater Sci. 2013, 58, 1388-1442; Zhao R et al. Energy Environ. Sci. 2012, 5, 9520-9527; Suss ME et al. Energy Environ. Sci. 2012, 5, 9511; Lee J et al. Energy Environ. Sci. 2014, 7, 3683-3689).
  • charging halfcycle charged ions or molecules are adsorbed by, and stored in, the electrodes.
  • the discharge half-cycle the stored charged species are released to a receiving solution or brine.
  • EIP electrochemical ion pump
  • circuit-switch In conventional electro- sorption, an electrode serves as the cathode and anode alternately within the same circuit and the switch is achieved by reversing the polarity of the applied voltage (Zuo K et al. Nature Reviews Materials, 2023, 8(7), 472-490; Srimuk P et al. Nature Reviews Materials, 2020, 5(7), 517-538). Such a switch of applied voltage direction is accompanied with the physical solution-switch, and they together demarcate the charging and discharge half-cycles (Figure 19).
  • An electrode in EIP also functions as the cathode and anode alternately, but by changing the counter electrode it pairs with.
  • an electrode in EIP is connected to two different electrodes in two different circuits in the charging and discharge half-cycles ( Figure 14c, Figure 14d).
  • a-EIP a complete circuit includes a flow channel sandwiched between two electrodes, a cation electrode (CE), and anion electrode (AE).
  • a-EIP a complete circuit includes a flow channel sandwiched between two electrodes, a cation electrode (CE), and anion electrode (AE).
  • the circuit N in red
  • the circuit N is connected through the feed channel where anions and cations are adsorbed by the anion electrode (electrodes i, anode) and cation electrode (electrode j, cathode), respectively, whereas electrode k functions as the anion electrode for circuit N+2.
  • the circuit N+l (in blue) connects electrodes j and k which release cations and anions to the brine channel, respectively, whereas electrode i functions as the cathode of circuit N-l and releases ions to the brine channel. Overall, each electrode shuttles ions from the feed solution to the brine.
  • a complete circuit comprises two cation electrodes, a feed channel, an anion exchange membrane (AEM), and a brine channel (Figure 14d).
  • Each cation electrode is shared between two circuits but is only connected to one circuit in every half-cycle.
  • circuit N in red
  • electrode j functions as the cathode in circuit N where electrode i serves as the anode.
  • Electrode j adsorbs cations from the feed channel while electrode i releases cations that it previously adsorbed from the feed channel of circuit N-l.
  • circuit N+l in blue
  • electrode j functions as the anode in circuit N+l where electrode k serves as the cathode.
  • Electrode j releases cations to the brine channel while electrode k adsorbs from the feed channel cations that it will release to the brine channel in circuit N+2 in the subsequent half-cycle.
  • anions migrate across the anion exchange membrane to maintain charge neutrality in both the feed and brine channels.
  • each electrode functions as the cathode of one circuit to adsorb cations from the feed solution in its charging half-cycle, and as the anode of another circuit to release cations to the brine in its discharge half-cycle.
  • the switch of an electrode between two adjacent circuits is achieved by electrical relays (Figure 14c, Figure 14d). This unique design of EIP replaces the slow physical solution-switch with the almost instantaneous circuit-switch.
  • the time scale to change electron flows is orders of magnitude shorter than the hydraulic residence time.
  • the s-EIP cell comprises two terminal electrodes, two anion exchange membranes, and a single cation electrode ( Figure 14e)
  • the a-EIP cell comprises two terminal electrodes, an anion electrode, and a cation electrode ( Figure 20a- Figure 20c and Note S3).
  • a constant current density (10 A nr 2 ) was applied in each circuit and near complete desalination of a representative brackish water (100 mM NaCl) was achieved with a current efficiency of -80% for both charging and discharge half cycles (Figure 14f and Figure 20b).
  • EIP electrode design The electrodes for ElP-based desalination should satisfy three major requirements (Figure 15a). First, the electrodes should enable fast transport of the target ions from the feed solution to the brine. Second, the electrodes should have minimal macropores to avoid direct mixing between the feed solution and the brine and to mitigate water transport via osmosis. Third, the electrodes should be electrically conductive to minimize resistive energy loss. Following these criteria, EIP electrodes were fabricated by applying a paste of activated carbon and ion exchange polymer (IEP) mixture on a titanium mesh current collector, followed by solvent removal and hot press to obtain a thin film of activated carbon with macropores filled by ion exchange polymer (Figure 15b, and Methods).
  • IEP activated carbon and ion exchange polymer
  • Another method for electrode preparation involves first coating a mixture of porous carbon, carbon black, and PVDF/or PTFE slurry onto a titanium mesh current collector. The solvent is then removed, followed by hot pressing to obtain a thin film electrode with macropores. Finally, a cation exchange polymer solution is sprayed onto the electrode surface, forming a dense ion exchange membrane layer.
  • the ion exchange polymer fillers are Nafion for cation electrode and quaternized poly(p-phenylene oxide) for anion electrode (Wang L et al.
  • the electrodes showed nearly perfect capacitive behavior based on their cyclic voltammograms and electrochemical impedance spectra with and without hot-press (Figure 23a- Figure 23b), with hot-press slightly reducing the capacitance and ohmic resistance.
  • the contribution of desalination to the overall voltage includes the voltage drops due to ion transport resistances in the diluate channel, the brine channel, one anion exchange membrane, as well as the voltage drop from the cation electrode/solution interface to the current collector (Figure 16c, Figure 25) (Wang L et al. Environ Sci Technol. 2019, 53, 3366-3378).
  • the distribution of the different contributions to the overall circuit voltage drop depends on multiple factors, including the current density, terminal electrode reactions, flow channel salinity, electrochemical properties of the cation electrode, and the half-cycle time.
  • the half-cycle time has substantial impacts on the behavior and performance of s-EIP.
  • concentration changes over time for both the diluate and brine appear to be continuous ( Figure 16d).
  • half-cycle time of 500s the periodic behavior of s-EIP clearly emerges, with salt removal from the diluate and salt release to the brine occurring in two distinct half-cycles ( Figure 16d).
  • the periodic s-EIP behavior also exists, but is macroscopically negligible, in s-EIP with short half-cycle time.
  • the observation of no concentration change in the solution outside the active circuit in an s-EIP with a half-cycle time of 500s confirms that the cation electrode exchanges ions dominantly with the solution within the active circuit.
  • half-cycle time Beside the periodicity of concentration change in solutions, varying half-cycle time also has a considerable impact on circuit voltage, and consequently, energy consumption.
  • the impact of half-cycle time on circuit voltage is particularly salient when charging at a relatively high current density with a long half-cycle.
  • the charging and discharge voltage profiles were similar when the half-cycle time was increased from 0.5s to 5s.
  • the circuit voltage at the start of the discharge half-cycle was appreciably lower with a half-cycle time of 50s and became very low ( ⁇ IV) with a half-cycle of 500s (Figure 16e).
  • the stored capacitive energy provided driving force for ion release in discharge, thereby reducing the applied circuit voltage needed to sustain the same current density as compared to the case where fewer ions and energy were stored in the cation electrode.
  • an s-EIP stack with 5 cation electrodes has 6 circuits in total and 3 active circuits at any moment (Figure 17b).
  • N the numbers of active circuits in the two half-cycles differ by one ( Figure 28).
  • the level of stacking is defined based on the number of cation electrodes, N, i.e., an s-EIP stack with N cation electrodes is referred to herein as an N- electrode stack.
  • the multi-electrode stacks can also be operated using either constant voltage (CV) or constant current density (CC) mode.
  • the circuit voltages for the charging and discharge half-cycles were 1.17 ⁇ 0.01 V and 1.28 ⁇ 0.01V, respectively ( Figure 17h).
  • these circuit voltages include contributions from the half-reactions of water electrolysis at the terminal electrodes, which is strongly corroborated by the circuit voltage distributions for multi-electrode s-EIP with a constant current operation.
  • the voltage for the middle circuit i.e., the circuit comprising only two CEs but not any terminal electrode, was only ⁇ 0.3 V, much lower than the voltages of the terminal circuits.
  • a 5-electrode s-EIP process with either constant current or constant voltage mode is far more efficient than conventional electro-sorption processes with solution-switch regardless of their configuration ( Figure 17k, Figure 31, Table 2).
  • s-EIP delivered a substantially lower SECi and/or a much higher ion flux.
  • s- EIP Although the amount of salt adsorbed per half-cycle in an s-EIP process is very small ( ⁇ 1 mg/g salt/electrode), s- EIP’s performance is superior to conventional electro-sorption processes with high-capacity electrodes that can adsorb more >100 mg/g salt/electrode, which supports the hypothesis that electrode capacity is irrelevant to separation performance if the limitations of solution-switch can be overcome.
  • sorption-based electrochemical separation can be operated using a circuit-switch strategy to enable unidirectional ion shuttling, ultrashort half- cycles, and greater performance in desalination.
  • circuit-switch By controlling electron flows instead of liquid flows, the use of circuit-switch in EIP overcomes major limitations of physical solution- switch in conventional electro-sorption, which translates to operational simplicity and performance enhancement.
  • EIP is demonstrated herein only for desalination, its general working principle should apply to other electro-sorption-based selective separation processes for contaminant removal as well as resource recovery and extraction, with a strong potential to enhance the separation performance in those applications.
  • a key to developing EIP for those applications lies in fabricating EIP electrodes with ion-selective electrode materials instead of activated carbon.
  • LIQUion dispersion LQ- 1115-1100 EW, 15% Nafion in a mixture of water and ethanol
  • Activated carbon (AC) powder with particle size of 5 ⁇ 1 um and surface area of 1800 ⁇ 100 m 2 g' 1 was purchased from XFNANO., Ltd., USA.
  • Titanium mesh (mesh size 100) was purchased from Jiangxin Wire Mesh Products Co., Ltd., China.
  • Graphite paper was purchased from Beijing Jinglong Special Carbon Technology Co. China.
  • Anion exchange polymer solution was prepared by dissolving quatemized poly(p-phenylene oxide) (QPPO, 10%) in a 1 : 1 dimethylacetamide/methanol mixture.
  • the cation electrode (CE) slurry included 20 wt% activated carbon (AC), 40 wt% LIQUion dispersion, and 40 wt% ethanol.
  • Anion electrode (AE) slurry was made of 10 wt activated carbon, 30 wt% QPPO solution, and 70 wt% methanol.
  • a slurry with ion exchange polymer and activated carbon particle was first coated on the center area of Ti-mesh current collector with a dimension of 60 mm x 60 mm, and then vacuum-dried at 60°C for 12 hours. After solvents have been removed, the cation electrode and anion electrode were pressed at 4000 psi with 140 °C and 160 °C, respectively. The mass loadings of cation electrode and anion electrode were both ⁇ 40 ⁇ 2 mg cm' 2 . The electrodes were framed with waterproof tape (3M, USA). The effective area exposed on both sides of the electrode was ⁇ 8 cm 2 .
  • cryogenic Focused-Ion Beam Scanning Electron Microscopy (FIB-SEM, Thermo Scientific, USA) was performed using a FEI Scios DualBeam FIB/SEM system. Sample stage was cooled down to -180 °C with liquid nitrogen to minimize beam damage to the sample. Cyclic voltammetry tests were conducted using an electrochemical workstation over a voltage window of -0.7 to 0.7 V, with a scan rate of 1 mV s' 1 . Platinum and Ag/AgCl electrodes were utilized as the counter electrode and reference electrode, respectively. The electrolyte solution contains 1 M NaCl.
  • the electrochemical impedances of the working electrodes were measured over a frequency range from 100 kHz to 10 mHz under open circuit potential.
  • the mass loading of the working electrode (10 mm x 10 mm) for the electrochemical test was ⁇ 40 mg cm' 2 .
  • the simplest s-EIP cell includes a pair of PTFE plates (as structural support), a pair of graphite terminal electrodes, two anion exchange membranes (AEMs), one cation electrode (CE), and four spacers. These components and their dimensions are described in Figure 32a- Figure 32c.
  • the circuit-switch between charging and discharge half-cycles is controlled by two relays.
  • the simplest a-EIP cell contains a pair of PTFE plates (as structural support), a pair of graphite terminal electrodes, two working electrodes (one cation electrode and one anion electrode) and three spacers.
  • Multi-electrode s-EIP stacks were assembled by stacking multiple repeating units with each unit containing, from left to right, an anion exchange membrane, a spacer, a cation electrode, and another spacer. These stacked repeating units are terminated by an anion exchange membrane, sandwiched between two terminal electrode flow channels each comprising a terminal electrode and a spacer.
  • An example of a 5-electrode s-EIP stack is illustrated in Figure 17b, with additional description of a 4-electrode s-EIP stack presented in Figure 28.
  • Conductivity, current and voltage were monitored with the Sensor Kit (Vernier Software & Technology, USA), which includes data collectors, conductivity sensors, current sensors, and voltage sensors.
  • the salt concentration was calculated based on a calibration curve relating conductivity to salt concentration.
  • Two key performance metrics were evaluated, including the ion flux, J t (unit: pmol cm' 2 min' 1 ), and the ion-specific energy consumption, SECi (unit: J pmol' 1 ).
  • the ion flux can be calculated using the following equation: where c , c d , and c b are the molar salt concentration in feed, diluate, and brine streams, respectively; v d is the volume of diluate; A is the effective electrode area; and t h is the halfcycle time.
  • the ion-specific energy consumption, SEC ⁇ can be evaluated using the following equation: where V c (i) and 7 d (i) are the circuit voltages for charging and discharge at current density i, respectively; V e (i) is the circuit voltage for the electrolytic cell at current density i; and the summation sign represents adding integrals from half-cycles over many cycles.
  • SECi When the contribution from electrolysis to SECi is excluded, SECi can be evaluated using the following equation: where V e (i) is the voltage drop due to electrolysis at current density i.
  • the brine remaining in the electrodes macropores mixes with the feed solution entering the flow channels, raising the concentration of the solution in the feed channel beyond the feed concentration at the start of the charging halfcycle.
  • Such mixing due to solution-switch compromises salt removal and increases energy consumption of electro- sorption for desalination.
  • asymmetric EIP asymmetric EIP
  • An asymmetric EIP (a-EIP) cell requires at least one cation electrode (CE), one anion electrode (AE), and a pair of terminal electrodes ( Figure 20a).
  • a-EIP does not require an anion exchange membrane.
  • the simplest a-EIP cell includes a pair of cation electrode and anion electrode, three circuits and three chambers. The electrolyte solution circulates in the chambers on both sides, which is identical to the s-EIP.
  • circuit 2 In the charging half-cycle, circuit 2 is connected, charging the cation electrode and anion electrode by capacitive adsorption of cations and anions, respectively, reducing the feed channel salinity.
  • circuit 1 and circuit 3 are activated simultaneously for ion desorption (electrode discharge).
  • Circuit 1 includes the terminal anode and anion electrode, where the anode undergoes oxygen evolution reaction (OER), and the anion electrode releases stored anions.
  • OER oxygen evolution reaction
  • circuit 3 the terminal cathode undergoes hydrogen evolution reaction (HER), and the cation electrode releases stored cations. Since the transfer of electrons on the terminal anode and terminal cathode must overcome the potential of the half-reaction of water electrolysis, the voltages of circuit 1 and circuit 3 are much higher than that of circuit 2 until the salinity in the feed (or diluate) channel becomes too low ( Figure 20b).
  • the calculated charging current efficiency was stable between 80% to 85%.
  • the electrolysis process also includes three contributions: oxygen evolution reaction (OER) at the terminal anode in the charging half-cycle, anions passing through the anion exchange membrane, and hydrogen evolution reaction (HER) at the terminal cathode in the discharge half-cycle.
  • OER oxygen evolution reaction
  • HER hydrogen evolution reaction
  • the net energy consumption from the desalination contribution in an s-EIP process can be obtained by subtracting the energy consumption of the electrolysis cell from the total energy consumption. With a current constant, the energy consumption is proportional to voltage.
  • V Desa i The contributions from desalination to the cell voltage (V Desa i) can thus be evaluated using the following equation: where V c (i) and V d (i) are the circuit voltages for charging and discharge at current density i, respectively; V e (i) is the circuit voltage for the electrolytic cell at current density i; and t h is the half-cycle time.
  • the summation sign represents adding integrals from half-cycles over many cycles.
  • the charge transfer in the new circuit comprises the capacitive desorption of the porous electrode and the hydrogen evolution reaction (HER) at the terminal cathode.
  • the OH' produced at the terminal cathode can pass through the anion exchange membrane into the brine, resulting in an alkaline pH in the brine stream.
  • higher current densities or extending the half-cycle time exacerbates the electrolysis of water at the terminal electrode.
  • higher current densities and longer half-cycle times lead to an increase in the potential of the cation electrode, making water dissociation or HER more likely to occur, resulting in an increase in pH of the diluate stream.
  • the occurrence of electrode side reactions also causes an observable decrease in the current density (Figure 27c).
  • circuit 2 With two cation electrodes, the new circuit formed by the two cation electrodes is dominated by capacitive adsorption/desorption (unless the electrode is saturated due to long-time charging at high current density). Therefore, for this new circuit (circuit 2), the required voltage to sustain the same current is substantially lower than that for the terminal circuit. As more cation electrodes are added to form an A-electrode s-EIP stack, circuits 2 to N-l all undergo capacitive adsorption/desorption, reducing the contribution of electrolysis at terminal electrodes to the overall energy consumption.
  • circuit 1 for example, all the current through terminal anode contributes to the oxygen evolution reaction (OER) and all the current through the counter electrode CE (CE #1, as the cathode) contributes to capacitive adsorption of Na Because the voltage drop for OER is significant compared to the applied voltage, the current density is low, and few ions are stored in the CE at the end of its charging half-cycle.
  • the anodic CE undergoes both capacitive desorption and OER, with the former consuming less energy and the later consuming more energy per charge transferred. Therefore, with the same applied voltage, the current density for circuit 2 is higher than that of circuit 1, and even more ions are stored in the cathodic CE (CE #2) of circuit 2. This cathodic CE of circuit 2 will later become the anodic CE of circuit 3 and undergoes even less electrolysis reaction and more capacitive adsorption, resulting in an even higher current density than circuit 2.
  • the cathodic terminal circuit (circuit N) and its adjacent circuits.
  • the cathodic terminal circuit has the lowest current density because the of its largest contribution of electrolysis to the circuit voltage.
  • Circuit N-l has a higher current density than the cathodic terminal circuit because of the larger contribution of capacitive adsorption/desorption to circuit voltage.
  • Combining the behaviors of anodic and cathodic terminal circuits and their adjacent circuits explain the roughly symmetric distribution of current density in a multi-electrode s-EIP stack. Under the same voltage, the CEs are better utilized (i.e., undergoing more capacitive adsorption/desorption and less electrolysis) the further away they are located from the terminal electrodes.
  • Table 1 Summary of literature data on charging time.
  • CDI capacitive deionization
  • MCDI membrane capacitive deionization
  • R-CDI rocking charging capacitive deionization
  • # It is assumed that the discharge time is the same as the charging time. Then, the ion flux obtained by recalculating from the total time; * SEC calculated by subtracting the energy consumed by electrolysis of water.
  • the devices and methods described herein can be used for (1) desalination and (2) selective separation to either remove or enrich specific ions using electrodes that can adsorb those ions with specificity.
  • the devices and methods described herein have advantages over capacitive deionization or conventional electrosorption (a process that has been commercialized) and even advantages over electrodialysis in some areas of selective separation.
  • An advantage of the devices and methods described herein is the way they operate, using “circuit switch” to replace “flow switch” to overcome many limitations in flow switch - based electro-sorption systems.
  • the devices can have a terminal electrode-free design.
  • a plate-and- frame stack has two terminal electrodes where electrolysis occurs to maintain the overall charge balance. Electrolysis typically costs substantially more energy than the capacitive adsorption/desorption occurring in the electrodes sandwiched between the two terminal electrodes.
  • Terminal electrode-free cell design is a tubular cell design with the goal of eliminating the terminal electrode. In such a design, all the capacitive electrodes (or ion exchange membranes in symmetric EIP) are arranged in a way that forms a circular crosssection. The working mechanism of such a system is the same as the asymmetric and symmetric EIP described above, but without the terminal electrodes and the associated electrolysis.
  • EIP electrochemical ion pump
  • EIP electrochemical ion pump

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Abstract

Sont ici divulgués des dispositifs de pompage d'ions électrochimiques et leurs procédés d'utilisation. Sont également divulgués la diffusion d'ions à travers une électrode et des films IBM. L'invention divulgue également des concentrations du diluat et de la saumure dans des expériences présentant une diffusion d'ions spontanée à travers une membrane échangeuse de cations (CEM) commerciale, une électrode cationique (CE) et une électrode d'électrosorption classique sans charge polymère échangeuse d'ions.
PCT/US2024/046645 2023-09-14 2024-09-13 Dispositifs de pompage d'ions électrochimiques et leurs procédés d'utilisation Pending WO2025059483A1 (fr)

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US20120082873A1 (en) * 2010-09-30 2012-04-05 Halbert Fischel Cross-flow electrochemical batteries
US20180241107A1 (en) * 2015-10-30 2018-08-23 Massachusetts Institute Of Technology Air-breathing aqueous sulfur rechargeable batteries
US20210388465A1 (en) * 2020-06-15 2021-12-16 Beijing University Of Chemical Technology Membrane electrode material, its preparation method and application in lithium extraction by adsorption-electrochemical coupling technology

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* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20120082873A1 (en) * 2010-09-30 2012-04-05 Halbert Fischel Cross-flow electrochemical batteries
US20180241107A1 (en) * 2015-10-30 2018-08-23 Massachusetts Institute Of Technology Air-breathing aqueous sulfur rechargeable batteries
US20210388465A1 (en) * 2020-06-15 2021-12-16 Beijing University Of Chemical Technology Membrane electrode material, its preparation method and application in lithium extraction by adsorption-electrochemical coupling technology

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